The research team surveyed 1,046 people who donated a kidney at their center between 1970 and 2011.

Of the 395 participants who wanted to buy or change health insurance after they donated a kidney, 15 were denied coverage, 12 were charged a higher premium and eight were told they had a pre-existing condition because they were kidney donors.

Of the 186 participants who wanted to buy or change life insurance after they donated a kidney, 23 were denied coverage, 27 were charged a higher premium, and 17 were told they had a pre-existing condition because they were kidney donors.

The study was published online July 16 in the American Journal of Transplantation.

"Kidney donors are among the healthiest individuals in the population. It's such a shame that some insurance companies are giving donors a hard time, often because of a misinterpretation that the normal biological changes that occur after donation are an indication of kidney disease," study author Dr. Dorry Segev said in a journal news release.

"This is a reminder that we need to remain strong advocates for our donors, and they need to remain strong advocates for themselves, educating insurance companies when these situations arise," Segev added.

Under the Affordable Care Act, live kidney donors can no longer be refused health insurance or charged higher premiums, the researchers noted.